Dual-Step Redox Engineering of 2D CoNi-Alloy Embedded B, N-Doped Carbon Layers Toward Tunable Electromagnetic Wave Absorption and Light-Weight Infrared Stealth Heat Insulation Devices

2D layered metallic graphite composites are promising electromagnetic wave absorption materials (EWAMs) for their combined properties of abundant interlayer free spaces, rich metallic polarized sites, and high conductivity, but the controllable synthesis remains rather challenging. Herein, a dual-step redox engineering strategy is developed by employing cobalt boron imidazolate framework (Co-BIF) to construct 2D CoNi-alloy embedded B, N-doped carbon layers (2D-CNC) as a promising EWAM. In the first step, a chemical etching oxidation process on Co-BIF is used to obtain an optimized 2D-CoNi-layered double hydroxide (2D-CoNi-LDH) intermediate and in the second, high-temperature calcination reduction is implemented to modify graphitization of the degree of the 2D-CNC. The obtained sample delivers superior reflection loss (RLmin) of -60.1 dB and wide effective absorption bandwidth (EAB) of 6.24 GHz. The synergy mechanisms of interfacial/dipole polarization and magnetic coupling are in-depth evidenced by the hologram and Lorentz electron microscopy, revealing its significant contribution on multireflection and impedance matching. Further theoretical evaluation by COMSOL simulation in different fields based on the dynamic loss process toward the test ring reveals the in situ EW attenuation process. This work presents a strategy to develop multifunctional light-weight infrared stealthy aerogel with superior pressure-resistant, anti-corrosion, and heat-insulating properties for future applications.

Multifunctional MoCx Hybrid Polyimide Aerogel with Modified Porous Defect Engineering for Highly Efficient Electromagnetic Wave Absorption

Traditional electromagnetic absorbing materials (EWAMs) are usually single functions and can easily affect their performance in diverse application scenarios. Effective integration of EWAMs into multiple function components is a valuable strategy to achieve maximum absorption and multifunction performance while maintaining their indispensable physical and chemical properties. In this work, the polyoxometalates (POMs) serving as "guests" are embedded within the Co-MOFs to construct 3d/4d-bimetallic based crystalline precursors of dielectric/magnetic synergistic system. The proper pyrolysis temperature induced the homogeneously distributed metallic Co and MoCx hetero-units into carbon matrix with modified porous defect engineering to enhance electromagnetic wave (EW). Owing to the brilliant synergistic effect of polarization, magnetic loss, and impedance matching, the superior RLmin of -47.72 dB at 11.76 GHz at the thickness of 2.0 mm and a wide adequate absorption bandwidth (EAB) of 4.58 GHz (7.44-12.02 GHz) covered the whole X-band at the thickness of 2.5 mm for η-MoC/Co@NC-800 are observed. More importantly, the resulting MoCx hybrid polyimide (MCP) aerogel exhibits desirable properties such as structural robustness, nonflammability, excellent thermal insulation, and self-cleaning capabilities that are comparable to those of commercially available products. This work offers inspiration and strategy for creating multipurpose microwave absorbers with intricate structural designs.

Universal F4-Modified Strategy on Metal-Organic Framework to Chemical Stabilize PVDF-HFP as Quasi-Solid-State Electrolyte

Solid-state electrolytes (SSEs) based on metal organic framework (MOF) and polymer mixed matrix membranes (MMMs) have shown great promotions in both lithium-ion conduction and interfacial resistance in lithium metal batteries (LMBs). However, the unwanted structural evolution and the and the obscure electrochemical reaction mechanism among two phases limit their further optimization and commercial application. Herein, fluorine-modified zirconium MOF with diverse F-quantities is synthesized, denoted as Zr-BDC-Fx (x = 0, 2, 4), to assemble high performance quais-solid-state electrolytes (QSSEs) with PVDF-HFP. The chemical complexation of F-sites in Zr-BDC-F4 stabilized PVDF-HFP chains in β-phase and disordered oscillation with enhanced charge transfer and Li transmit property. Besides, the porous confinement and electronegativity of F-groups enhanced the capture and dissociation of TFSI- anions and the homogeneous deposition of LiF solid electrolyte interphase (SEI), promoting the high-efficient transport of Li+ ions and inhibiting the growth of Li dendrites. The superb specific capacities in high-loaded Li.

High-Density Nanopore Confined Vortical Dipoles and Magnetic Domains on Hierarchical Macro/Meso/Micro/Nano Porous Ultra-Light Graphited Carbon for Adsorbing Electromagnetic Wave

Atomic-level structural editing is a promising way for facile synthesis and accurately constructing dielectric/magnetic synergistic attenuated hetero-units in electromagnetic wave absorbers (EWAs), but it is hard to realize. Herein, utilizing the rapid explosive volume expansion of the CoFe-bimetallic energetic metallic triazole framework (CoFe@E-MTF) during the heat treatment, the effective absorption bandwidth and the maximum absorption intensity of a series of atomic CoFe-inserted hierarchical porous carbon (CoFe@HPC) EWAs can be modified under the diverse synthetic temperature. Under the filler loading of 15 wt%, the fully covered X and Ku bands at 3 and 2.5 mm for CoFe@HPC800 and the superb minimum reflection loss (RLmin ) of -53.15 dB and specific reflection loss (SRL) of -101.24 dB mg-1 mm-1 for CoFe@HPC1000 are achieved. More importantly, the single-atomic chemical bonding among Co─Fe on the nanopores is captured by extended X-ray absorption fine structure, which reveals the formation mechanism of nanopore-confined vortical dipoles and magnetic domains. This work heralds the infinite possibilities of atomic editing EWA in the future.